# cptts2.f man page

cptts2.f —

## Synopsis

### Functions/Subroutines

subroutinecptts2(IUPLO, N, NRHS, D, E, B, LDB)CPTTS2solves a tridiagonal system of the form AX=B using the L D LH factorization computed by spttrf.

## Function/Subroutine Documentation

### subroutine cptts2 (integerIUPLO, integerN, integerNRHS, real, dimension( * )D, complex, dimension( * )E, complex, dimension( ldb, * )B, integerLDB)

**CPTTS2** solves a tridiagonal system of the form AX=B using the L D LH factorization computed by spttrf.

**Purpose:**

```
CPTTS2 solves a tridiagonal system of the form
A * X = B
using the factorization A = U**H*D*U or A = L*D*L**H computed by CPTTRF.
D is a diagonal matrix specified in the vector D, U (or L) is a unit
bidiagonal matrix whose superdiagonal (subdiagonal) is specified in
the vector E, and X and B are N by NRHS matrices.
```

**Parameters:**

*IUPLO*

```
IUPLO is INTEGER
Specifies the form of the factorization and whether the
vector E is the superdiagonal of the upper bidiagonal factor
U or the subdiagonal of the lower bidiagonal factor L.
= 1: A = U**H *D*U, E is the superdiagonal of U
= 0: A = L*D*L**H, E is the subdiagonal of L
```

*N*

```
N is INTEGER
The order of the tridiagonal matrix A. N >= 0.
```

*NRHS*

```
NRHS is INTEGER
The number of right hand sides, i.e., the number of columns
of the matrix B. NRHS >= 0.
```

*D*

```
D is REAL array, dimension (N)
The n diagonal elements of the diagonal matrix D from the
factorization A = U**H *D*U or A = L*D*L**H.
```

*E*

```
E is COMPLEX array, dimension (N-1)
If IUPLO = 1, the (n-1) superdiagonal elements of the unit
bidiagonal factor U from the factorization A = U**H*D*U.
If IUPLO = 0, the (n-1) subdiagonal elements of the unit
bidiagonal factor L from the factorization A = L*D*L**H.
```

*B*

```
B is REAL array, dimension (LDB,NRHS)
On entry, the right hand side vectors B for the system of
linear equations.
On exit, the solution vectors, X.
```

*LDB*

```
LDB is INTEGER
The leading dimension of the array B. LDB >= max(1,N).
```

**Author:**

Univ. of Tennessee

Univ. of California Berkeley

Univ. of Colorado Denver

NAG Ltd.

**Date:**

September 2012

Definition at line 114 of file cptts2.f.

## Author

Generated automatically by Doxygen for LAPACK from the source code.

## Referenced By

cptts2(3) is an alias of cptts2.f(3).

Sat Nov 16 2013 Version 3.4.2 LAPACK